1. Field of the Invention
The invention relates to a self-adjusting clutch assembly, in particular for commercial vehicles or tractors, as well as to a method for operating a clutch assembly.
2. Description of Related Art
Clutch assemblies having a multi-plate clutch are already known.
These known clutch assemblies which are used in the case of commercial vehicles or tractors, have a driving clutch as well as a clutch for additional implements. These clutches are operable separately through a clutch pedal or through a hand lever.
These known clutch assemblies are suitable for use in vehicles where a separate clutch is to be provided for driving and a separate clutch is to be provided for the implements.
These known clutches all have the drawback that when the clutch discs wear out the operating point of the clutch is shifted so that the release force required to operate the clutches varies accordingly.
The object of the invention is therefore to provide a clutch assembly for a multi-plate clutch as well as a method for operating a multi-plate clutch which can be produced cost-effectively in a structurally simple manner and which has an improved release characteristic, more particularly a more constant release characteristic with a high operating accuracy over the entire service life.
Thus according to the invention it is proposed to design a clutch assembly, more particularly a clutch assembly for a motor vehicle, such as a commercial vehicle or a tractor, with at least a self-adjusting clutch device with at least one clutch disc and at least two contact pressure plates.
The clutch assembly preferably has a clutch disc which can be coupled, more particularly with keyed engagement, to two contact pressure plates.
It is also preferable if the clutch assembly has a number of clutch discs, such as for example two clutch discs which can each be coupled, more particularly with keyed engagement, to one or more contact pressure plates.
The invention is particularly advantageous because the operating force of the clutch assembly can be kept within a predetermined tolerance band as a result of the self-adjusting device of the clutch assembly or of the clutches. The width of this tolerance band is preferably aimed at zero.
According to a particularly preferred embodiment of the invention a device is provided which keeps the installation position of a plate spring substantially unchanged throughout the entire wear on the lining and thus keeps the release force of the clutches, more particularly of two clutches, unchanged and guaranteed throughout the service life. The plate spring thereby preferably loads pressure plates which act on the linings or the discs.
This device which keeps the installation position of the plate springs substantially constant preferably has at least one cast ring and at least two sheet metal tapered rings wherein one of these sheet metal tapered rings is connected rotationally secured to a pressure plate, more particularly to the pressure plate on the transmission side. This device also preferably has two circumferentially mounted compression springs which in the event of wear at least partially or under predetermined conditions turns one of the tapered rings relative to the other tapered ring until the wear in the axial direction is compensated. This device is preferably coupled to a driving clutch or to a clutch on the transmission side.
In a particularly preferred embodiment during activation of the clutch through an operating mechanism, for example through a lever, the cast ring is displaced in the axial direction, with a stepped bolt or friction device causing a pressure plate to lift off from the friction lining or disc. More particularly the friction force applied to the stepped bolt is greater than the operating axial compression spring forcexe2x80x94according to the geometry of the taper.
It is preferable if, in the event of wear on the clutch disc on the engine side or on the transmission side, as a result of force applied by a plate spring a contact pressure plate, more particularly a pressure plate on the engine side, draws the stepped bolt through the bolt head of this stepped bolt out from the friction device and thus release a gap at a shoulder or ledge of the stepped bolt.
Then preferably when operating a clutch, more particularly a clutch on the transmission side, through a lever the cast ring is moved up to the shoulder or to the ledge of the stepped bolt so that the tapered rings can be turned relative to each other under the action of a compression spring force acting on at least one of these tapered rings, preferably on both tapered rings, so that the wear in the axial direction is compensated and the plate spring swings back again in its original installation position. The level of the release force of the clutch device thus corresponds again to the level in the new state or in the substantially unworn state.
Thus according to the invention an assembly of several clutches is provided wherein the release characteristic of at least two of these clutches is constant or unchanged over the entire service life of the clutches or at least an element of these clutches. An element of this kind over the service life of which the release characteristic of the clutch or the release characteristics of the clutches is constant is in particular at least a disc or at least a clutch lining of the clutch assembly.
The element over the service life of which the release characteristic of the clutch or clutches is constant is preferably an element which has the fundamental property of influencing the release characteristic of the clutch assembly.
It is proposed for example that an element, such as for example a friction lining or a disc is provided which when changed or shifted in position would or does basically influence the release characteristic of the clutch or one of the clutches. Despite the presence of such an element the release characteristic is preferably kept substantially constant. This is achieved for example in that the influence which the thickness of the friction lining or the thickness of the discs has on the release characteristic is substantially compensated by a self-adjusting device.
According to the invention it is thus proposed that a clutch assembly having at least one clutch disc and at least two contact pressure plates is provided with an adjustment device for compensating at least in part changing or changed operating conditions of the clutch device.
By operating conditions of the clutch assembly are meant here in particular the characteristic values of the clutch assembly or characteristic values which characterise the operating process of the clutch assembly. By way of example the operating time for releasing the clutch or the operating force or the time path of the operating force or the like can be considered as an operating condition.
It is also preferable if predetermined operating conditions or predetermined operating characteristic values are set whereby when these are changed or at the start of a change the adjustment device triggers, more particularly independently or automatically, measures for compensating this change. According to the invention it is preferable if the adjustment device controls or regulates predetermined positions or relative positions of structural elements.
This problem is further solved by a clutch assembly having at least one clutch disc and at least two pressure plates.
Thus according to the invention it is proposed to provide a clutch assembly with at least one spring device, more particularly a plate spring device, wherein the position of the plate spring device can be controlled or regulated by a control or regulating device. The plate spring device thereby preferably acts on the contact pressure plate. The plate spring device thereby preferably acts on the contact pressure plates so that the pressure plates when the operating device for operating the clutch is not activated are pressed against the friction linings or the discs of the clutch assembly so that the clutches are substantially in a closed state.
It is however also preferred if when the operating device of the clutch assembly is not activated the spring device or the plate spring device holds one or more of the pressure plates in an opened state so that the relevant clutch is substantially opened.
Two contact pressure plates are thereby preferably provided to form when the clutch is closed a positive, more particularly a keyed, connection with the clutch discs or friction linings. The plate spring device thereby preferably tensions the contact pressure plates between the clutch discs.
It is thereby preferred if a predetermined operating characteristic is maintained within a predetermined interval with a predetermined interval length by the regulating device or control device. More particularly it is preferred if the operating characteristic is maintained within an interval so that a maximum permissible upper deviation and a maximum permissible lower deviation is defined for each operating point. It is also preferable if the maximum upper deviation and the maximum lower deviation agree with each other and is substantially the same for all operating points of the operating characteristic.
It is preferred if the interval length of the interval aims at being zero so that the operating characteristic is actually maintained substantially constant.
According to a particularly preferred further development of the invention the clutch assembly is provided with at least one adjustment device by which at least one clutch characteristic value can be regulated in dependence on the wear on the clutch, more particularly the wear on the clutch discs or linings.
An adjustment device is preferably provided by which in dependence on at least one operating characteristic value, such as for example the spring force existing in a predetermined state of the plate spring device, at least a further characteristic value of the plate spring device can be adjusted so that the spring force of the plate spring device is regulated substantially to a predetermined value under predetermined conditions.
Thus according to the invention it is proposed for example that the position of the plate spring device under predetermined conditions is displaced in dependence on the spring force of the plate spring device so that the spring force of the plate spring device again assumes its original value. It should be noted that predetermined conditions hereby preferably exist. By way of example a predetermined position is set of the pressure plates (e.g. extreme position) or a predetermined position of the operating lever of the operating device of the clutches (e.g. extreme position).
According to a particularly preferred embodiment of the invention the adjusting device or the self-adjusting device for adjusting the clutch device or the clutches is designed to be path-controlled.
According to a particularly preferred embodiment of the invention the clutch device has at least one operating device, such as for example an operating lever, for operating the clutch. It is preferable if separate operating devices are provided for the different clutches, i.e. more particularly for different spots at which the force flow can be selectively interrupted or closed. It is also preferable if a single operating device, such as for example a single operating lever or the like is provided for operating several clutches.
According to a particularly preferred embodiment of the invention during the course of the self-adjusting process of the clutch assembly, or clutch devices, a force equilibrium is set, more particularly increasing. It is also preferred if with a path-controlled adjustment device during the self-adjusting process a force equilibrium is increasingly set. By way of example the position of a plate spring device is hereby regulated or controlled whereby the force applied by the plate spring device interacts with other forces so that a force equilibrium is set.
A particularly preferred clutch assembly according to the invention has n clutch discs and/or m clutches and/or p pressure plates wherein n, mxcex5N and pxcex5Nxe2x89xa72.
A clutch assembly according to the invention preferably has two clutches which in a particularly preferred embodiment are both self-adjustable.
It is particularly preferred if the clutches, more particularly the two clutches, are self-adjusting by an identical adjustment device. It is thereby particularly preferred if the self-adjusting process is substantially in part identical substantially independently of the identity of the worn clutch discs.
By way of example in the event of wear on any one clutch disc or any one friction lining a plate spring device adopts a position which it would likewise adopt if wear of a similar amount were to appear on any other clutch disc or any other friction lining or if the sum of the wear on several clutch devices would correspond to this wear. In the adjusting process the original position or installation position of this plate spring device for example is produced again so that independently of where the wear has occurred, during the adjustment process a substantially identical first position of the plate spring device is changed each time into a likewise substantially identical second position of the plate spring device.
According to a particularly preferred embodiment of the invention the clutch assembly or the clutches has/have n clutch discs and p pressure plates wherein an adjustment device is related to the p pressure plates. By this is meant that the adjustment device takes into account the potential wear occurring on each friction face of a clutch disc which forms a friction-locking connection at least at times with one of the p pressure plates so that the relevant clutch is closed.
According to a particularly preferred embodiment of the invention the adjustment or self-adjustment of the clutch assembly is carried out under predetermined conditions. By way of example the adjustment or self-adjustment is always carried out when the clutch is released.
It is also preferred if the self-adjustment is undertaken during engagement of the clutch.
According to a particularly preferred embodiment of the invention a device is provided for preventing uncontrolled adjustment of the adjustment device. A device of this kind has for example a pin, such as a bolt or a stepped bolt. A device of this kind for preventing an uncontrolled adjustment of the adjustment device is preferably designed as a friction device and/or as a clamping device. It is thereby ensured by a friction and/or clamping device of this kind that an adjustment is only possible under predetermined conditions, such as for example in the presence of predetermined force conditions.
These predetermined forces can be determined for example by geometric conditions, such as in particular the geometric conditions of the clutch discs, thus e.g. the question of the presence or absence of wear.
According to a particularly preferred embodiment of the invention adjustment is carried out (automatically) so that with the clutch closed the pressure plates apply each time substantially a constant force on the clutch discs throughout the service life.
A motor vehicle with clutches according to the invention preferably has at least one driving clutch and/or at least one clutch for assemblies.
According to a particularly preferred embodiment of the invention the adjustment device has at least a first and a second device wherein the first device releases an area in the event of wear on at least one of the clutch discs. By way of example a lash or play is produced in the event of wear. This area or this play is eliminated or compensated again by the second device for removing the wear-conditioned influence on predetermined operating characteristic values of the clutch or clutch adjustment process under predetermined conditions, thus in particular at predetermined time points or under predetermined conditions. By way of example an element, such as a stepped bolt, is mounted with friction engagement in a contact pressure plate. The friction engagement existing between this bolt or this element and the pressure plate can thereby be overcome under predetermined conditions whereby a relative displacement of the element opposite the pressure plate is produced in particular by a first (part) device. This relative displacement preferably corresponds to the wear which has appeared on at least one of the clutch discs.
As a result of this relative displacement of the bolt opposite the pressure plate the bolt also changes its position relative to a further element, such as for example a further plate aligned parallel with the pressure plate.
In order to compensate the wear-conditioned influences on the clutch process the relative displacement which the bolt has undergone relative to the additional plate, such as intermediate plate, is then compensated under predetermined conditions by a second device. The relative position of the further plate (intermediate plate) opposite the aforementioned pressure plate is hereby preferably changed.
The relative displacement between the further plate (intermediate plate) and the pressure plate thus preferably also corresponds to the wear which has appeared.
If now for example the distance has changed between at least one of two friction linings and at least one of two clutch discs, since at least one of these clutch discs has worn, then for example the path change between these clutch discs is compensated through a change in the spacing between an intermediate disc and a pressure plate whereby the interspace between the friction linings is filled out more particularly by a series connection of the pressure plate, the intermediate plate and a spring device, such as plate spring device, and where applicable further substantially rigid elements.
According to a particularly preferred embodiment of the invention the clutch assembly according to the invention has at least one sensor device for detecting a relative movement between different pressure plates. This sensor device detects more particularly a changed relative position of the pressure plate under predetermined conditions, By way of example this sensor device detects a changed maximum spacing between the pressure plates. This maximum spacing is for example determined by the spacing of two friction linings or discs. The spacing changes as a result of the wear on these friction linings.
According to a preferred embodiment of the invention this sensor device has at least one bolt. It is also preferred if the sensor device or adjustment device is coupled to at least one operating element for operating at least one of the clutches so that the adjustment or detection of a relative movement is automatically undertaken during operation of this operating element.
According to a particularly preferred embodiment of the invention the sensor device is coupled to at least one component part which is moved during an operating process of one of the clutches in dependence on the operating movement.
A component part of this kind is for example an intermediate lever.
According to a particularly preferred embodiment of the invention the adjustment device and/or the sensor device has at least one clamping or friction device. A clamping or friction force is preferably applied by a friction or clamping device of this kind. This clamping or friction action is provided in particular to connect elements which are or are to be coupled together under first conditions and which are to be mounted movable relative to each other under second predetermined conditions.
By way of example a clamping or friction connection of this kind is provided between a bolt, more particularly a stepped bolt, and one of the pressure plates.
It is preferable if a predetermined clamping or friction force can be applied by the friction or clamping device and which is produced for example by a fitting with oversize, such as a close tolerance or transition fit, or by means of a spring device or the like.
By way of example the friction or clamping device has a clamping screw which, screwed in axially or circumferentially, applies in the radial direction a clamping force on a bolt device. A screw of this kind is screwed into the pressure plate for example and contains in its inner space a bolt device or stepped bolt device. It is also preferred if a clamping screw of this kind is formed as a type of clamping sleeve.
It is preferred if a substantially adjustable clamping force or friction force can be applied by the clamping screw or sleeve or friction or clamping device.
By way of example a substantially constant clamping force can be applied throughout the service life by the clamping or friction device or the clamping screw or sleeve whereby this clamping force is exerted preferably on a bolt device, such as a stepped bolt device and thus holds this stepped bolt device always fixed opposite the pressure plate when the relative force between the pressure plate and stepped bolt is less than a relative force, which is predetermined in terms of direction and size, between the stepped bolt and this pressure plate.
According to a particularly preferred embodiment of the invention the clamping screw and/or the clamping sleeve is a component part which is slit substantially lengthwise at least in part or is slit with a longitudinal component. This component part is slit in screw fashion for example. A slit of this kind makes it possible for example for the walls of the clamping screw or clamping sleeve to move radially inwards when biased by radial force and thus to apply a clamping force.
It is preferable if the clamping force is overcome under predetermined conditions when wear appears on at least one of the clutch devices. By way of example the clamping force is overcome immediately if wear has occurred, so that a relative displacement takes place between the bolt and pressure plate. It is also preferred if the bolt device slides relative to the pressure plate at another point in time.
According to a particularly preferred embodiment of the invention the bolt embraced by the friction or clamping device is a stepped bolt which has different diameter ranges so that an axial stop is formed.
According to a preferred embodiment of the invention a second stop can be additionally provided to restrict movement in a second axial direction, and is mounted more particularly on the stepped bolt, for example in the form of a bolt head.
According to a particularly preferred embodiment of the invention the bolt device which is embraced by the friction or clamping device is arranged so that it runs substantially axially movable through a first pressure plate and an intermediate plate which is mounted between a first and second pressure plate.
It is preferable if the aforementioned stops or ledges serve as a stop for this first pressure plate and this intermediate plate.
According to a particularly preferred embodiment of the invention the bolt device is secured against slipping out. More particularly the bolt device is secured against slipping out from the contact pressure plates or the intermediate plate.
According to a particularly preferred embodiment of the invention an intermediate device, such as for example an intermediate plate, is mounted spatially between the first and second pressure plate, with the intermediate plate being held through a friction device at a certain distance from the second pressure plate, and this distance being variable in the event of wear. A plate spring device ensures for example force is applied on the pressure plates in the direction of the relevant clutch disc or friction lining, whereby the plate spring device is mounted between the first pressure plate and the intermediate plate.
According to a particularly preferred embodiment of the invention the intermediate plate, as also preferably the pressure plate, is mounted axially movable wherein it is particularly preferred if under predetermined conditions the movement of the intermediate plate is blocked or prevented in at least one orientation.
By way of example the movement is blocked in a first orientation if the second pressure plate adjoins the one disc or a friction lining.
According to a particularly preferred embodiment of the invention the adjustment device has an overrunning type device or an overrun which adjusts the clutch assembly under predetermined conditions,. More particularly this adjustment takes place for example at least at times in the event of wear on the friction linings. The overrunning device is mounted for example between the intermediate plate and the second pressure plate. It is preferable if this overrunning-type arrangement in the event of movement in a first direction increases the distance between the intermediate plate and the second pressure plate, whilst the movement is blocked in the counter direction.
Under predetermined conditions, more particularly at least at times, the overrun can be moved in its overrunning direction so that the distance between the intermediate plate and the second pressure plate increases.
In a corresponding way an adjustment device can also be mounted for example between the plate spring device and one of the pressure plates or between the pressure plates.
A corresponding device which is likewise designed for example as a type of overrun, for increasing the distance, which is arranged between the force introduction points of the spring device or plate spring device, is also preferred.
According to a particularly preferred embodiment of the invention the adjustment device has at least two elements which contact one another and which in the event of a predetermined movement or with a predetermined introduction of force or force direction execute a movement relative to each other which leads to a change in the spacing, more particularly to an increase in the spacing in a predetermined direction.
According to a particularly preferred embodiment of the invention one of these two elements is biased by an energy accumulator device, such as a spring. This spring force is counteracted under first predetermined conditions or circumstances by a counter force so that a relative displacement of the two elements of the adjustment device is substantially avoided. Under second predetermined conditions or circumstances, the counter force decreases at least so that the two elements of the adjustment device move relative to each other under the action of the spring force or a part of the spring force.
The two aforementioned elements of the adjustment device are for example the already mentioned tapered rings. By way of example these tapered rings change their axial spacing as a result of their facing inclines during rotation. It is preferable if detents are provided on the slopes of these tapered rings to engage in each other so that a reduction in the spacing of the rings is substantially prevented by the detent formation.
It should be noted that other spacers or fixing devices can also be provided in place of or as an addition to the detents.
The surface contour, particularly on the slope side, of the tapered rings is preferably formed with a linear rise. It is also preferred if this surface contour is curved or follows an exponential function. Other functional or non-functional surface contours are also preferred.
According to a particularly preferred embodiment of the invention the change in the axial spacing of the tapered rings in the event of their rotation corresponds to the play which is to be compensated. More particularly it is preferred if the tapered rings have a linear surface rise wherein a is the pitch angle of this linear rise and tan a corresponds to the play which is to be compensated.
It is also preferable if the surface contour on the slope side of the tapered rings which preferably rotate relative to each other is different and follows for example different functions.
According to the invention it is preferred if each of the pressure plates when the clutch is closed contacts precisely a clutch disc or precisely a friction lining. It is also preferred if a pressure plate contacts different friction linings when the clutch is closed. By way of example when the clutch is closed a pressure plate contacts two different friction linings simultaneously. It is also preferable if a pressure plate for closing a first clutch contacts a first pressure plate and for closing a second clutch contacts a second pressure plate. It is further preferred if the pressure plate or pressure plates is or are formed with variable thickness.